Optical code division multiplexing receiving device and time gate processing method in optical code division multiplexing receiving device

Abstract

Technology is provided in which, by performing time gate processing using a clock signal with time jitter suppressed, time and intensity fluctuations which in the prior art had been observed in auto-correlated signals after time gate processing are reduced. In a decoder, received optical code division multiplexed signals are divided into two, one of which is reflected as a decoded signal, and the other of which is transmitted as an encoded signal in the encoded state. In the clock extraction circuit, encoded signals are divided into first encoded signals and second encoded signals. In the first clock signal generation portion, first clock signals are generated from the first encoded signals, and optical pulses synchronized with the first clock signals are extracted from the second encoded signals, and second clock signals are generated from the extracted optical pulses. In the time gate processor, time gate processing of the decoded signal is performed, using the second clock signals as the gate signals, and the result is output.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] This invention relates to an optical code division multiplexing receiving device, and to a time gate processing method in the optical code division multiplexing receiving device. [0003] 2. Description of Related Art [0004] In order to increase communication capacity, Optical Time Division Multiplexing (OTDM), Wavelength Division Multiplexing (WDM), Optical Code Division Multiplexing (OCDM), and other optical multiplexing technologies, in which a plurality of channels of optical pulse signals are transmitted together in a single optical fiber transmission path, are being studied. Among these optical multiplexing technologies, OCDM has the excellent characteristic that there is no limit to the number of multiplexed channels when multiplexing optical pulse signals. [0005] Using OCDM communication, transmission is performed as follows. On the transmitting side, codes which are different for each channel are used to enco...

AI Technical Summary

Benefits of technology

[0035] By means of an optical code division multiplexing receiving device of this invention, and a time gate processing method of this invention in the optical code division multiplexing receiving device, by generating a clock signal from encoded signals in the encoded state, time jitter and intensity jitter in auto-correlated signals after time gate processing, which have been observed in the prior art, can be reduced.

[0037] In this way, using a limiting amplifier for generating the first clock signals, intensity jitter thereof can be further reduced. Furthermore, in generating the second clock signals, by using a clock reproduction circuit, time jitter thereof can be further reduced.

[0039] With such a configuration, only the wavelength component necessary for clock extraction is passed, and unnecessary wavelength components can be eliminated.

Problems solved by technology

Here, in the optical pulse signals obtained as a result of decoding, cross-correlated signals result in so-called interference noise.

When the number of multiplexed signals increases due to encoding, interference noise due to cross-correlated signals increases, so that the error rate for encoded signals increases.

However, in a conventional OCDM receiving device as disclosed in Literature 2, clock signals are extracted from decoded signals, and so the clock signals have substantial time jitter.

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